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R Ihl

Publications and source records attributed to R Ihl.

At least 37 records · Page 2Linked to original sources
PubMed1993

Segmentation of the spontaneous EEG in dementia of the Alzheimer type.

Studies on EEG data in dementia of the Alzheimer type have mainly investigated parameters in the frequency domain. However, the EEG also reflects the momentary functional state of the brain. The EEG can be partitioned into segments of spatially stationary map landscapes as characterized by the locations of potential maxima and minima, to study the time domain of the EEG. We calculated the segment structure of 19-channel EEG recordings (1-30 Hz) from 10 patients with dementia of the Alzheimer type and 10 sex-matched geriatric controls. The EEG maps corresponding to global field power peaks were used for analysis. The locations of the potential maximum and minimum of the maps were determined over the course of 20 s and used for segmentation. The segments of EEG activity were significantly fewer (p < 0.05) and the segments lasted longer (p < 0.05) in patients compared to controls. This effect could be observed over the whole period of recording and thus was not caused by only a few long segments. The data may be linked to morphological and biochemical findings of neuronal loss and loss of synapses in dementia of the Alzheimer type.

Aged↗
PubMed1992

Differential validity of psychometric tests in dementia of the Alzheimer type.

Forty-nine patients with a clinical diagnosis of probable dementia of the Alzheimer type underwent an extensive test battery designed to evaluate cognitive deficits according to NINCDS/ADRDA criteria. All patients demonstrated signs of impairment on this test battery. One day later, they were administered a second test battery that consisted of the Mini-Mental State Examination (MMS), the Alzheimer's Disease Assessment Scale (ADAS), the SKT test (SKT), and the Brief Cognitive Rating Scale (BCRS) to assess the construct validity, sensitivity, and possible shortcomings of these tests. A control group of 47 age-matched persons was administered the same test battery to allow a comparison with reference values from other studies. Due to the design of the study, values of controls and patients did not overlap. Intercorrelations in patients were above 0.65 (p < 0.05 after Bonferroni correction) for all four cognitive tests. The ADAS and BCRS appeared to document the whole course of the disease in patients studied. The best differentiation with the SKT test could be obtained in mild to moderate dementia; however, due to the test's construction, a floor effect demonstrated its limitations in the case of severe dementia. Results obtained with the MMSE indicated the contrary: a ceiling effect showed its lack of differentiation in mild dementia. Therefore, a combination of tests should be used in the evaluation of cognitive deficits in the course of dementia of the Alzheimer type.

Activities of Daily Living↗
PubMed1992

[Importance of the EEG in early and differential diagnosis of dementia of the Alzheimer type].

The development of new parameters in the quantitative evaluation of EEG provides new diagnostic opportunities for the clinician. Reviewing all published papers on EEG and dementia over the last 10 years revealed 30 out of 428 studies discussing EEG alterations in relation to the severity of the disease. This approach provides useful information for early and differential diagnosis of dementia. Besides a generalised slowing-down represented by an increase of delta and theta and a decrease of alpha and beta in the frequency spectrum (also characterised by a reduction of the peak frequency), the topography of the alterations changes depending on the severity of the disease. For instance, the alpha activity loses its normally occipital orientation. In early stages of the disease, it is measured parietally ("anteriorized"). In advanced stages, the activity is equally distributed over the scalp. Some studies found significant alterations even in early stages of the disease, most pronounced in theta and beta activity, making the EEG a useful tool for the early diagnosis of dementia. But studies on the differential diagnostic value are lacking. The value of EEG could be improved after parameters like the EEG segmentation or the traditional parameters combined with cognitive stimulation have been sufficiently evaluated.

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PubMed1991

Integrity of the blood-CSF barrier in dementia of Alzheimer type: CSF/serum ratios of albumin and IgG.

Serum and cerebrospinal fluid (CSF) from 25 patients with dementia of Alzheimer type (DAT) and 25 controls were assayed for concentrations of albumin and IgG. The severity of dementia was rated with the Mini Mental State Examination. The CSF/serum ratio for albumin and IgG as well as the IgG index were used to evaluate blood-CSF barrier function in the respective groups. The control group was matched for age, sex and the indirect alcohol parameters, mean corpuscular volume and gamma-glutamyltranspeptidase. There were no signs of dysfunction of the blood-CSF barrier for proteins or signs of local synthesis of IgG in the central nervous system (CNS) of the demented patients. The permeability of the blood-CSF barrier appeared to be unrelated to dementia severity. The data do not support the hypothesis that a pathological leakage through the blood-CSF barrier facilitates the entry of extraneuronal proteins to the CNS, which might contribute to the pathophysiological process in DAT.

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PubMed1991

Topography of the quantitative electroencephalogram in dementia of the Alzheimer type: relation to severity of dementia.

Conventional electroencephalographic (EEG) frequency bands and peak frequency were investigated in patients with probable dementia of the Alzheimer type (DAT). Measures of EEG topography and activity were also related to the severity of dementia, as assessed by neuropsychological tests. EEG activity measured in conventional frequency bands proved to be the most sensitive parameter for the quantitative differentiation of DAT, whereas the topography of peak frequency was the better qualitative discriminator between healthy subjects and DAT patients.

Aged↗
PubMed1990

Endocrine responses to growth hormone releasing hormone and corticotropin releasing hormone in early-onset Alzheimer's disease.

In a study of the hypothalamic-pituitary-somatotropic (HPS) and the hypothalamic-pituitary-adrenal (HPA) systems in early-onset Alzheimer's disease (AD), 10 drug-naive patients and matched controls were given 50 micrograms growth hormone releasing hormone (GHRH) at 9 a.m. and 100 micrograms corticotropin releasing hormone (CRH) at 6 p.m. as an i.v. bolus dose. Compared with controls, patients with AD showed attenuated GHRH-induced growth hormone (GH) responses and decreased adrenocorticotropic hormone (ACTH) but normal cortisol secretion following CRH. GH responses to GHRH were negatively correlated with the plasma insulin-like growth factor (IGF-I) concentrations and the severity of dementia. A positive correlation was found between GHRH-evoked GH release and ACTH responses to CRH. The results suggest a pathological process at the level of the pituitary or the hypothalamus, possibly involving a cholinergic, monoaminergic, or peptidergic imbalance in AD, and support the view that altered HPS and HPA secretory dynamics in AD are related to the underlying brain dysfunction.

Adrenocorticotropic Hormone↗
PubMed1988

[Topography of P300 in psychiatry--II. Cognitive P300 fields in dementia].

The P300 wave undergoes alterations during physiological aging showing lower amplitudes and longer latencies in geriatric controls. By means of topographical display of P300-data it could be shown that the topography with maximal positivity at parietal sites is maintained in aging. In patients, however, suffering from senile dementia of Alzheimer's type signs of a frontal elevation and a parietal decrement of P300 amplitudes could be observed. The findings can be interpreted firstly as an indication that the frontal lobe is less effected. On the other side if a hippocampal dipole is assumed a neuronal lesion could lead to a turn of this dipole with the result of a now frontally located positivity.

Adult↗
PubMed1988

[The topography of P300 in neuropsychiatric pharmacotherapy. III. Cognitive P300 fields in an organic psychosyndrome (Wilson's disease) before and during treatment with D-penicillamine].

Beside senile dementia of Alzheimer's type (SDAT) there are also dementive syndromes due to a disturbance in metabolism. In a case with a disturbance of copper metabolism (Wilson's disease) a similar P300-pattern was found as described in SDAT with signs of a frontal amplitude elevation. Under therapy with d-penicillamine the frontal P300-positivity moved from frontal to parietal structures. Combined with this migration was an amelioration in cognitive function. This single-case study underlines the significance of P300-topography in the evaluation of therapy effects in dementive disorders.

Adult↗